1. Field of the Invention
The present invention generally relates to an image forming apparatus that connects to plural AC sources.
2. Discussion of the Background
In recent years, electric power consumption of image forming apparatuses has been increasing, resulting from image forming apparatuses including color input/output functions and improved operation speed. An image forming apparatus including color input/output functions requires an actuator configured to form plural images, and a controller that controls the actuator. An image forming apparatus with improved operation speed requires an improved action speed and torque of devices configured in the image forming apparatus, for example of the motor, etc. Such requirements in image forming apparatuses for color input/output functions and increased operation speed result in increased electric power consumption. An image forming apparatus generally receives electric power from an electric power socket, for example that has a capacity of 100V15 A in Japan.
If an image forming apparatus requires more electric power, the image forming apparatus may need to receive electric power from an electric power socket with the capacity of, for example, 100V20 A, or a power source voltage of an image forming apparatus may need to be 200V. Office facilities may not have such capacities. If an office facility does not have such capacities then an image forming apparatus may access plural AC sources with plural power source cords.
JP 2003-244853A proposes an image forming apparatus that interrupts the supply of AC power source to a main part of an image forming apparatus to secure a proper operation, if one power source cord is connected to the AC source but another power source cord is not connected to the AC source. Such an image forming apparatus can spread a load and assign the spread load for an AC consumption unit and an AC/DC converter for supplying the electric current from the plural electric cords. Such an image forming apparatus includes an AC relay on the AC source supplying line of the power source cord. The AC relay is turned ON if a DC load side of an AC line is active and a coil is receiving current. On the other hand, the AC relay does not turn ON if the DC load side of the AC line is not active and the coil is not receiving current. With that operation the image forming apparatus can operate electrically securely when the AC side of the power source cord is connected to the AC socket.
JP 2003-323085A proposes an image forming apparatus that can supply electric power efficiently to plural loads from plural power source cords even with a changing demand of electric power. The image forming apparatus therein changes a load of a supplying AC power source from a power source cord in accordance with plural modes that have different requirements of consumption of electric power. Such an image forming apparatus supplies electric power to a first heater from a first power source cord and supplies electric power to a second heater from a second power source, if when the mode is started the sum of electric power consumption of the plural heater exceeds a predetermined value. Such an image forming apparatus also supplies electric power to the first heater and the second heater from the first power source if in the mode the sum of electric power consumption of the plural heaters is below the predetermined value.
JP 2005-121681A proposes an image forming apparatus that can supply electric power efficiently and determine properly any error condition in an electric power control element. Such an image forming apparatus includes a main power source and a sub-power source. The image forming apparatus supplies electric power to a DC load, for example a CPU, etc., from the main power source. The image forming apparatus also supplies electric power to a side of an AC load, for example a fixing roller. Such an image forming apparatus display a prompt for an operator to connect to the sub-power source if the AC source detecting circuit detects no supply of electric power from the sub-power source and the image forming apparatus does not determine a solid state relay (SSR) error condition if the CPU receives an error signal from a SSR error detecting circuit. In other words, such an image forming apparatus determines an error of an electric power control element or interception of an AC source when the image forming apparatus detects an error of an electric power control element.
The image forming apparatuses as discussed above have the following drawbacks. First, a structure of an image forming apparatus including has two power source cords is more complicated than a structure of an image forming apparatus including only one power source cord. A control and structure of an image forming apparatus with two power source cords has to address a situation in which one power source cord is unconnected. If in such a situation one power source cord is unconnected, the image forming apparatus with two power source cords may not work normally. It also becomes difficult for an operator to determine the cause of such a problem, because this structure is more complicated, and thereby at least it typically requires more time for a user to determine such a problem.